Levi

Known as humanity's most powerful soldier. He is a clean-freak. While it is said that he is blunt and unapproachable, it is noted that he has a strong respect for structure and discipline. The rumors are that he was originally part of underground crime before he became a soldier. He often comes off as unfriendly, but he cares for his team deeply and has never undervalued human life.

Note: Levi is the official English translation by Kodansha and it is also used in the mangaka's blog.